


hot springs episode

by spasticbirdie



Category: Undertale (Video Game)
Genre: Alphyne, Alphynecentric, F/F, Hot Springs & Onsen, Oral Sex, Smut, Trans Alphys, Trans Character, can you believe it? i wrote smut! i did it!, it's 3 AM TIME FOR ME TO SLEEP AND REGRET THIS IN THE MORNING
Language: English
Status: Completed
Published: 2016-08-31
Updated: 2016-08-31
Packaged: 2018-08-12 04:15:12
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,775
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/7920130
Author URL: https://archiveofourown.org/users/spasticbirdie/pseuds/spasticbirdie
Summary: <blockquote class="userstuff">
              <p>Undyne takes Alphys on a very steamy date.</p>
            </blockquote>





	hot springs episode

Alphys shivered a little. Waterfall wasn’t exactly cold, but it was definitely no Hotland, and any dip in the temperature hit Alphys like an ice cube down her spine. She had been about to spend another evening alone in her lab, catching up on anime and eating instant noodles, when Undyne had called her up and demanded to know what she was doing tonight. When Alphys answered something along the lines of “nothing,” Undyne had hung up, appeared on her doorstep less than a minute later, and insisted they go for a walk.

 

“Undyne-” Alphys nearly tripped over a root, then regained her balance and squinted at the trail. The glow from the flowers and mushrooms gave off a good amount of light, but Alphys still had trouble seeing the path ahead of her. “Why are out here, anyways?” she continued.

 

“Fresh air!” Undyne threw an arm around Alphys’ shoulder and pulled her close. “You’re cooped up in that lab all day, you need to get out more!”

 

“Uhhh huh.” Alphys wondered exactly how ‘fresh’ the air could be when they were underground. She almost tripped over another root, grabbed onto Undyne for a moment, then steadied herself and let go, blushing. “Where are we even going?”

 

“You’ll seeeeeeeeeee…” Undyne cut ahead of Alphys on the path and hurried ahead. Before long, she had disappeared into the tall grass. Alphys groaned and pushed into the grass after her.

 

It only took her seconds to get lost in the shifting grass. “Undyne?” Alphys heard some sort of splash off to her left, and followed the sound. “Where’d you-”

 

She trailed off as she came out of the grass and broke into a clearing. It was a small pond, not much larger than an average swimming pool. It was surrounded by rocks, giving it a sort of natural wall that made it hard to see inside without peeking over them. A thin layer of steam rose off the glowing blue water.

 

“Undyne?” Alphys cautiously approached the pond and peered over the rim. Suddenly, bubbles began to rise from the water.

 

Before she could get back, Undyne erupted from the water with a huge splash, soaking Alphys. “Tadaaaaaaa!” She ducked back down, only her head sticking out of the water.

 

“It’s….a pond?” Alphys tried to shake herself dry.

 

“Nope! It’s a hot spring!” Undyne swam over to the water’s edge and rested her head on the rocks. “I know you always say you can’t swim because the water’s too cold, and then I found this place and I thought it’d be perfect!”

 

Alphys leaned over and dipped a hand in the water. Sure enough, the water was comfortably warm to the touch. She wondered how this spring had got here; most of the water in Waterfall flowed from Snowdin, meaning it was usually fairly cold. She swished her hand around, making ripples across the still surface. Maybe some volcanic vein from even deeper than the Underground surfaced here? Or some tectonic shift between Hotland and Waterfall created a stream of heat that cut under the-

 

“So....are you gonna come swimming or what?” Undyne asked.

 

“Oh, uh…” Alphys withdrew her hand from the water. “Well, if you had told me  _ this _ was what you wanted to show me I would’ve brought a bathing suit, but-”

 

“Well…” Undyne pushed back from the edge of the spring, still only poking her head out of the water. “I didn’t bring a bathing suit either, y’know.”

 

Alphys didn’t understand what she meant, until she saw Undyne’s clothes lying in a pile on the other side of the spring. Her jacket, shirt, bra, jeans, p-

 

“Oh.” Alphys wasn’t even in the water yet and she had already gone red as the magma that was heating the waters. “U-um…”

 

Alphys deliberated at the edge of the spring for a moment, then hurried behind one of the larger rocks. “C-c-can you keep a l-l-lookout for a second?”

 

“Oh, sure!” Undyne swam to the edge and began to pull herself out.

 

Alphys let out a strangled squeak and covered her eyes. “A-a-a-a-a-actually it’s okay! It’s okay, I’ll just change fast!” She ducked behind the rock, and seconds later, her lab coat, t-shirt, and sweatpants were draped over it. After a moment of hesitation, a pair of white-and-pink striped panties and a plain white bra joined them.

 

Then nothing. Undyne waited, treading water. “Uh, Alphys? Are you coming?”

 

“I-I-I’m not c-coming in until you look away!”

 

Undyne laughed. “Well maybe i’ll just come out to get you, how about that?”

 

There was a moment of quiet, then Alphys clambered over the rock and jumped in as fast as humanly possible, hitting Undyne with a huge splash. Covering her chest, she surfaced.

 

Undyne shook the water from her hair and grinned. “Nice cannonball.”

 

“Mnrf.” Alphys blew bubbles in the water, sulking a little.

 

“So? What do you think?”

 

Alphys had to admit, the water felt amazing. She had been working in the lab all day, but after less than a minute in the spring she felt all the stress in her body disappear. She sank down and basked in the warmth for a while, soaking up the heat of the spring, occasionally moving and sending little ripples across the surface.

 

After a while, she surfaced. “Hey Undyne-”

 

She looked around. Undyne had vanished. “Undyne?”

 

Suddenly, she felt a pair of muscular arms wrap around her stomach. “Right here,” said a voice right in her ear.

 

Alphys nearly jumped right out of the water, and she quickly covered her chest. “H-h-hey!”

 

Undyne laughed. “I’ve been under the water for, like, five minutes, Alphie. Was wondering when you’d notice.”

 

“N-not funny.” Alphys pouted. Undyne laughed and hugged her a little tighter, pulling her over to the edge of the spring and lying against the rocks.

 

Alphys felt Undyne’s chest press against her back, and suddenly felt a warmth that had nothing to do with the spring. She curled her tail up, trying to make herself as small as possible. Maybe she could just slip out-

 

“You know-” Undyne’s hands began moving upwards from Alphys’ stomach. “You don’t have to cover up like that.” She leaned down, nuzzling Alphys’ neck, and whispered, “It’s not like it’s anything I haven’t seen before.”

 

Alphys responded by wrapping her arms a little tighter around her chest, if only because she felt like her heart was beating a mile a minute and it would burst right out if she didn’t hold it in.. “I-I-I…”

 

Between the warmth of the water and the equal warmth of Undyne pressing so close to her, forming coherent words felt like too much for Alphys’ head.

 

So did keeping her arms hugged to her chest, her head decided, and she slowly let go, her arms floating freely, her chest uncovered. It wasn’t uncovered for long, though, as Undyne’s hands slid up from Alphys’ stomach to her chest. Her breathing sped up as Undyne cupped her breasts in her hands, gently massaging them.

 

Undyne snickered, kissing her neck. “It’s really cute how sensitive you are, y’know.”

 

“S-stoppit…” Alphys squirmed a little as Undyne rubbed circles on her nipples.

 

Undyne laughed quietly and dug her teeth gently into Alphys’ neck. “Make me.”

 

Alphys would have tried, but as she said that Undyne drifted one hand off her chest and slowly began tracing it back down her body; running it over her hip and the base of her tail, then to her thigh, and finally slowly bringing it up to her groin, giving her balls a gentle squeeze. Still nipping at Alphys’ neck and tweaking one of her nipples, Undyne grasped Alphys’ dick and began slowly stroking up and down.

 

The stimulation all over her body was almost too much for Alphys. Her breathing became ragged, speeding up as Undyne stroked her faster and harder. Then she slowed down, bringing her hand to the tip of Alphys’ dick and running one finger in a circle around the head. She kept switching up her speed, sometimes stopping to fondle Alphys’ balls.

 

Eventually, Undyne took a firm grasp of Alphys’ shaft and began stroking at a gradually increasing pace. Alphys squirmed in the water, but Undyne held her tightly. Alphys squirmed with pleasure in her grasp, her tail swishing through the water.

 

Just as Undyne began to feel Alphys twitching in her grip, she felt a hand suddenly flailing for hers, guiding it off her dick. Alphys gripped Undyne’s hand tightly as she slowly relaxed, her dick still erect.

 

Undyne nuzzled Alphys’ neck, this time gently and without teeth. “You okay?”

 

“Yeah…” Alphys sounded breathless, like she had come to the brink, stopped and stayed for a moment, and then slowly backed down. “It’s just…”

 

She trailed off. “Just what?” Undyne prompted.

 

Alphys fidgeted. “I didn’t… I didn’t want to get the water, uh, dirty.”

 

Undyne stared for a moment, then burst out laughing.

 

Alphys went a little redder. “H-hey, this could be a really delicate ecosystem! W-we shouldn’t even be in the water, what if we upset the ph balance or s-something…”

 

Undyne tried to calm her laughter. “Well, if you want to keep the water clean…”

 

She let go of Alphys, who floundered a bit in the water before grabbing the rocks again. Slipping out from behind her, Undyne swam out across the spring, first in a breaststroke, then slowly turning over and floating on her back for a moment, showing her front. Alphys’ eyes wandered across her exposed chest, her eyes moving down to her tight, sculpted abs, and then her hips and toned legs.

 

Then she slipped underwater, disappearing in the steam. A few seconds later, Alphys felt Undyne’s hands rest on her thighs.

 

Before she could wrap her head around what was happening, she felt Undyne’s mouth wrap around the head of her dick, making her gasp. In normal circumstances it would have felt warm, but compared to the heat of the spring the inside of her mouth felt almost cool. The change in temperature was a whole different kind of stimulation, and after Undyne’s handjob earlier, Alphys felt ready to blow.

 

So when Undyne took a firm hold of Alphys’ butt and shoved her head forward, taking as much of Alphys’ dick into her mouth as she could, Alphys’ hips bucked in response, and she failed completely to hold it in. 

 

When Alphys finally relaxed, panting and spent, Undyne surfaced. She slowly swallowed, licked her lips, and then stuck her tongue out cheekily. “Man, I’ve never been more glad to have gills.”

 

“Sh-shut up!” Alphys giggled a little, despite herself.

 

Undyne swam up to Alphys and snuggled up against her. For a while, they just lay there and cuddled, watching the steam curl into the air.

 

“So, what’s the verdict on the spring?” Undyne asked.

 

Alphys nuzzled Undyne’s neck. “A l-little too hot for m-me, I think.”

 

“Aww.” Undyne gave Alphys a last little kiss on the cheek, and began climbing out of the spring. “Anyway, I wanted to show this to you before I told anyone else. Maybe we could get Catty and Bratty to come down, have a girls night out or something like that.” Undyne squinted into the darkness. “Ugh, where’d my clothes go…”

 

“Oh, they’re-”

 

Alphys stopped short. Undyne was almost completely out of the spring now, lying over the rocks as she searched for her clothes. As she felt around for them in the grass, she pulled a little further out of the spring, her firm, toned butt up in the air.

 

“Do you see them anywhere, Alphys? Damn…”

 

“Um....”

 

“C’mon, gimme a hand here!”

 

“Uh…”

 

Well, Alphys reasoned, it’s only fair.

 

“Hey, Alphys, you - haaaahh…?”

 

Taking a tentative grip on Undyne’s ass, Alphys spread Undyne’s legs and pressed her snout between them, at first just breathing in Undyne’s warmth.

 

Feeling Alphys’ breath waft between her legs, Undyne felt a warmth and wetness that had nothing to do with the water. Then the gentle feeling of Alphys’ breath was replaced with the feeling of her tongue lapping gently at her vagina, and Undyne felt her legs buckle a little.

 

“F-fuck, Alphys…” Undyne tried to formulate a more coherent statement, but failed miserably. “Hold on, j-just a second, shit…” Undyne pulled away for a brief moment, flipped onto her back, then quickly pulled Alphys’ face back into her crotch. “Fuuuuuuuuuuuuuckkkkkk....” was all Undyne could manage before devolving into primal panting and moaning as Alphys went to work.

 

After slowly running her tongue over Undyne’s slit, Alphys spread it slightly with her fingers and gently worked her tongue inside, slowly pushing it in and out. For once, Alphys felt very, very glad for her long tongue. She began to speed up, and starting playing with Undyne’s clit with a free hand.

 

“Nnnnngh!” Undyne clawed at Alphys’ head as her back arched slightly, relaxed, and then arched again. Alphys withdrew her tongue and slipped her fingers in, her lips moving upwards; first kissing and giving a quick tonguing to Undyne’s clit, then kissing her waist, her abs, and stopping for a while at her chest, kissing a nipple lightly before taking it in her mouth and sucking down on it, all the while still working her fingers in and out of Undyne’s wet slit.

 

Undyne began tightening up on Alphys’ fingers. “A-Alphys, A-Al-Aaaah, f-fuck!”

 

And right then, Alphys pulled her fingers out. Undyne, her hips feeling numb but her orgasm teetering on the brink and slowly falling, could only catch her breath. “Alphys…” She felt for Alphys’ hand and took it, trying to guide it back to her aching slit, but Alphys firmly guided her hand away before kissing her, tongue slipping suddenly and surprisingly roughly into Undyne’s mouth. At the same time, Undyne felt Alphys pull close, locking her hips against Undyne’s and grinding her dick against Undyne’s pussy.

 

Alphys broke away from their kiss for a moment, panting. “Are...are you okay, uh, w-with-”

 

Undyne cut her off by grabbing Alphys around the neck with one hand, pulling her back into a deep kiss, while taking Alphys’ dick with the other hand and guiding it downward, until the tip was pressing against her slit. Alphys gave a few tentative prods, went as far as her head, then slowly pushed deeper until her hips were grinding up against Undyne’s.

 

Undyne moaned deeply into Alphys’ mouth and clenched up, her hips shaking as she finally tipped over the edge. Alphys felt an additional warmth wash over her shaft and pressed close to Undyne, letting her ride out her orgasm.

 

As Undyne relaxed, Alphys pulled away from the kiss, suddenly feeling awkward. “D-do you...uh...want me to p-pull-”

 

And again, Undyne cut her off by pulling her back to that same deep kiss, before grinding her hips against Alphys’. Alphys relaxed and gave herself over to everything; Undyne’s tongue coiling with hers, Undyne’s body being as close as it could be to hers, and the warmth of Undyne’s pussy around her dick. She began slowly pulling out and then, just as slowly, pushing back in, bringing everything but the tip of her dick out before pushing back in, all the way to the base.

 

As she sped up, soon Alphys began to moan into Undyne’s mouth. Thrusting in and out with more and more ferocity, Alphys had to break away from their kiss to pant heavily and take deep, shaky breaths. Undyne felt Alphys twitching inside her, close to the edge.

 

“U-Undyne, I’m-”

 

Undyne pulled Alphys close, grinding her hips right against Alphys’. “Do it… do it, fuckkk!”

 

“Nnnnn!” Alphys made one last thrust as she erupted deep inside Undyne, clenching up as she came. Undyne bit her lip as she felt the warm feeling seep through her, and Alphys riding her orgasm. She pulled out, spent, and nearly collapsed on top of Undyne.

 

“Hah...hah...o-okay…” Alphys tried to make a coherent sentence, failed, and just gave up, resting her head against Undyne’s chest.

 

Undyne nuzzled her head and planted a small, soft kiss on her. “You good?”

 

Alphys took in and let out a deep breath, then snuggled up against Undyne, the two of them lying at the edge of the spring.. “I-I’m good. I’m great.”

 

Undyne wrapped her arms around her small, scaly girlfriend. “Me too.”

 

“Mmm.”

 

The two lay there for a while, watching the steam rise off the water.

 

“Hey, uh, Undyne?”

 

“Yeah, Alphie?”

 

“Um…” Alphys said through slightly chattering teeth. “I’m kinda cold.”

 

“Oh!” Undyne felt Alphys shiver slightly in her arms. “Um. Let’s, uh, get clothes on.”

 

“Uh, yeah.”

 

* * *

 

“So, what do you think? Nice place?”

 

“Y-yeah. Really nice.”

**Author's Note:**

> WOW MY FIRST SMUT  
> i didn't really edit or beta this at all i'm posting this at 3 am before my better sense kick in so any errors are a result of my exhausted inspiration


End file.
